1. Field of the Invention
The invention relates to a measuring system, and more particularly to a measuring system for a tensile or compressive test.
2. Description of the Related Art
In general, tensile or compressive tests are used to test the resistance capability for a material that sustains loading (tension) in a quiescent state or increasing state. In a tensile test, two extremities of a test sheet are clamped and the tension along the axial directions are applied to the two extremities of the test sheet, such that the test sheet is lengthened along a direction parallel with the acting force. In a compressive test, two extremities of a test sheet are clamped and pressure along the axial directions are applied to the two extremities of the test sheet, such that the test sheet is shortened along a direction parallel with the acting force.
FIG. 1A shows a conventional measuring system which uses a single camera to measure the displacements of two extremities of an object to be tested. As shown in FIG. 1A, a camera 110 is coupled to a personal computer (PC) 130 and simultaneously captures the variations of the labels A and B of an object 120. In the measuring system, the camera 110 must be disposed apart from the object 120, so as to capture the label A and the label B at the same time. Therefore, each pixel of the camera 110 may represent a longer distance than actual, such that the image resolution obtained by the PC 130 is inaccurate, thus causing measurement errors. FIG. 1B shows another conventional measuring system which uses two cameras to measure the displacement of two extremities of an object to be tested, respectively. In the measuring system, the two cameras 110 and 110B are used to measure the variations of the labels A and B of an object 120, respectively. Thus, a higher image resolution is obtained due to each camera capturing only one label. However, using two cameras increase costs.